Stroboscope



April 13, 1933- w. D. COCKRELL 1,904,124

STROBOSCOPE Filed Aug. 27, 1932 Inventor: William D. Cockrell His Attorneg.

Patented Apr. 18, 1933 UNITED STATES PATENT OFFICE WILLIAM. D. COCKBELL, OF SOHENEC'I'ADY, NEW YORK, ASSIGNOB T GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW-YORK STBOBOSCOPE Application filed August 27, 1832. Serial No. 680,711. I

My invention relates to stroboscopes and it has for its object the provision of an improved constructionof stroboscope which is adapted for operation at high speed, is reliable and has a small power demand. My invention will be better understood from the following description taken in connection with the accompanying drawing, and its scope will be pointed out in the appended claims.

In the single figure of the drawing which is a circuit diagram illustrating one embodiment of m invention, a source of direct current supp y, which forexample may be 250 volts, is shown at 1 and 2. Connected across this source of supply is the voltage divider 3 and the potentiometer 4, the former having taps 5 and 6. Connected in series between the supply lead 1 and the point 5 of the divider is the reactor 7 having a relatively high reactance, such for example as 50 henries, and the capacitor 8 whose capacitance, for example, may be 10 mfd. Capacitor 8 by reason of its connection with the supply circuit is charged tlirough the reactor 7 to the potential difference between the lead 1 and the point 5 of the divider. At regular intervals the capacitor 8 is allowed to discharge through the are or electron discharge device 10, which during its operation emits light which illuminates the rapidly rotating disk 11 carrying a series of dark radial bands 12. The device 10 is operated for only a very short interval since the capacitor 8 quickly discharges and the potential applied to the device drops to a value below the ionizing potential thereof. Because of the great rapidity of the discharge of the capacitor 8 there is insuflicient time for the potential supplied from the supply circuit through the reactor 7 to rise sufliciently high to cause the device 10 to continue its operation after the capacitor 8 has become discharged. The tendency of device 10 to continue to conduct to a potential below its operating potential and the stray inductance in its anode circuit causes the capacitor to discharge to a very low potential before the device ceases to conduct and if the control grid of the device has by this time be- 50 come negative, the tube will cease conducting. Capacitor 8 following each discharge recharges through the reactor 7. In order to produce a greater illumination of the disk 11 than that obtained from device 10 I have shown the are or electron discharge device 14, connected in the anode circuit of device 10 in shunt with the resistor 15, which for example ma have a value of 10,000 ohms. Resistor 16 is also shown in the anode circuit of device 10 to limit the discharge current of the device to a safe value, but the use of such a resistance may not be found necessary in all cases.

Control of the grid of device 10 may be eflected by various means. In the form which I have chosen to illustrate in the present case, grid control is effected by the interception of a light beam. Light from the source 18 is caused to pass through a focal point by means of the lenses 19 and 20 and is then directed on a photo-electric device 21, such as a photo' electric tube. At the focal point of the light beam I have shown by way ofillustration the wheel 22 having spokes which as the wheel turns rapidly intercept the light beam. In the form illustrated the wheel 22 has thesame number of spokes as disk 11 has radial bands 12, it being assumed that the disk and the wheel rotate at approximately the same speed. Byconnection with the divider 3 at 6 the photo tube 21 controls the grid of the electron discharge device 23. The anode of this tube connects with the lead 1 of the supply circuit through the reactor 24 and limiting resistor 25 and the cathode connects with the arm of the potentiometer 4. The resistor may be used alone ifdesired, although for best resultsI prefer to use a reactor also.

The operation of the apparatus will now be described. During the short interval that the light beam from lamp 18 passes between two adjacent spokes of Wheel 22 into the photo tube 21 the device 23 ofiers a minimum impedance to the flow of current in its anode circuit and the grid of device 10 is thereby held'negative with respect to its cathode. Hence device 10 is not conducting and no light is thrown on the disk 11 from either devices 10 or 14. At the instant the the voltage applied to the anode of the device 10 is insufficient to cause that device to continue to conduct since current from the supply circuit is unable to rise through the reactor 7 rapidly enough to cause device 10 to continue in operation. By the time that the device 10 has become extinguished the spoke of wheel 22 which intercepted the light beam will have passed on and the beam become reestablished thereby causing the grid of .device 10 to become negative. Capacitor 8 now recharges through the reactor 7 and becomes completely charged before the next spoke of wheel 22 intercepts the light beam. Thus each successive spoke of wheel 22 by intercepting the light beam causes devices 10 and 14 to simultaneously flash producing a momentary illumination of disk 11. If this disk and the wheel 22 are rotating at exactly the same speed the radial bands 12 on the disk will appear to stand still. If, however, there is a slight difierence in rotating speeds of these two members, the bands will appear to move forward or back ward in accordance with the relative speeds of the members in a well known manner.

I have chosen the particular embodiment described above as illustrative of my invention and it will be apparent that various other modifications may be made without departing from the-spirit and scope of my invention which modifications I aim to cover by the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. A stroboscope comprising a source of supply of direct current, a reactor and a capacitor arranged in series and connected with said source, a vapor electric discharge de-v vice connected to be energizedfrom said capacitor and provided with a control grid and means for controlling the charge on said grid.

2. A stroboscope comprising a source of supply of direct current, a reactor and a capacitor arranged in series and connected with said source, a vapor electric discharge lamp connected to be operated by the discharge from said capacitor, and grid control means for initiating the operation of said lamp.

3. A stroboscope comprising a source of supply of direct current, a reactor, a caoacisupply of direct current, a reactor, a capacitor connected to be charged through said reactor from said source, a grid controlled vapor electric discharge device connected across said capacitor, a resistor in circuit with said device, adischarge lamp connected across said resistor and means for intermittentily supplying a positive charge to said gri 5. A stroboscope comprising a source of supply of direct current, a voltage divider connected across said source,'a reactor and capacitor connected in series across a portion of said divider, a grid controlled vapor electric discharge device connected across said capacitor and a photo-electric tube and amplilziier therefor connected to control said grl In witness whereof, I have hereunto set my hand.

WILLIAM D. COCKRELL.

5 DiS LAnMER,

1,904,124.William D. Geclcrell, Schenectady, N. Y. Smososcorn. Patent dated April 18, 1933. Disclaimer filed February 20, 1935,. by the essignee, General Electric Company. 7 v V Herehy enters the following disclaimer to claims I, 2,.end-3 of the said Letters Potent, which are in the following words, to wit:

I l. A strohoscope comprising a source of supply of direct current, areactorend e capacitor arranged in series and connected with said source, a, vapor electric daze charge device connected to be energized from said capacitor and provided WitWe control grid and means for controllingthe charge on seid grid.

2. A stroboscope comprising a, source ofsuppl of direct current, 9. reactorsnd s cc ecitcr erre ed in series and connected Wit said source 3 wt or electric P 11g a discharge lamp connected tobe operated. by the discharge from said. capacitor, and grid control means for initiating the operation of said lamp.

'3. A strohoscope compris' esource of supplyof' direct current, a reactor; o capacitor connected to be cherg fthrough seid reactor from said source, a lid con trolled vapor electric discharge device arranged, to beqenergized by the ischerge from seid'cepacitor and means for intermittently supplying s positive charge to said grid! I Gazette March 19, I935}. 

